Cerebroside sulfotransferase (EC 2.8.2.11) is a membrane-bound enzyme involved in the synthesis of sulfatide, a galactolipid enriched in myelin. Sulfatide is implicated in maintaining the integrity of the myelin membrane, and disturbances in the metabolism of sulfatide have profound clinical effects. Thus knowledge of the mechanism and regulation of synthesis of this lipid is extremely important. Cerebroside sulfotransferase has been studied in the central nervous system, but because it is most active during the early stages of development when only small amounts of tissue are available, we have purified the enzyme 2,000-fold from rat kidney, and have prepared an antibody to it. With the purified enzyme and antibody we plan to purify the cerebroside sulfotransferase from the central nervous system (CNS), study the relationship of the CNS and kidney enzymes, localize the enzyme in the kidney by microscopic immunocytochemical studies, and study the appearance of the immunoreactive protein during developmet and correlate it with appearance of catalytic activity. The activity of the enzyme in brain changes during development, increasing with myelination and subsequently decreasing as the rate of myelin synthesis declines. By comparing immunoreactive activity with enzyme activity we plan to determine whether a proenzyme is present before the appearance of catalytic activity and whether the developmental changes in activity are due to alterations in the amount of enzyme protein in the cell. The enzyme activity may also be regulated by naturally occurring inhibitors within the cell. Thus possible inhibitors of the enzyme will be studied; this is especially important as these inhibitors may find some therapeutic use in metachromatic leukodystrophy. Finally, our studies should enable us to determine whether the enzymes from kidney, CNS, and peripheral nervous system, known to be under different genetic control, are in fact identical proteins.